function login() {  
  
    var username = document.getElementById("username");  
    var pass = document.getElementById("password");  
  
    if (username.value == "") {  
  
        alert("请输入用户名");  
  
    } else if (pass.value  == "") {  
  
        alert("请输入密码");  
  
    } else if(username.value == "abc" && pass.value == "123456"){  
  		alert("用户验证成功，正在为你跳转到！");
         window.location.href="welcome.html"; 
  
    } else {  
  
        alert("请输入正确的用户名和密码！");  
  
    }  
	
	
	}